In many telecom and information technology applications, hot pluggable modules are desired. A hot pluggable module is an electronic module that provides any number of different functions, but which can be plugged into a system without removing power from the system. In other words, it can be inserted into a hot or powered receptacle that is designed to couple the module to the system.
Modules for telecom applications may need to operate from either a +24 volt or −48 volt power supply provided at the receptacle and therefore need to correct the polarity of the supply. They should exhibit minimum power losses or heat dissipation, and should provide for dual voltage (24 and 48) start-up/shutdown threshold control. Such modules should also provide some form of start-up delay and should control or limit their inrush current. Further, the modules should hold up during supply drop-out; that is, block reverse current flow.
Existing power input circuits for modules can be quite complex, yet do not provide all of these desired features.